A package structure and method of forming the same are provided. The package structure includes a first die, a second die, a wall structure and an encapsulant. The second die is electrically bonded to the first die. The wall structure is laterally aside the second die and on the first die. The wall structure is in contact with the first die and a hole is defined within the wall structure for accommodating an optical element insertion. The encapsulant laterally encapsulates the second die and the wall structure.